Electronic analog safety for automatic weapons



April 10, 1956 e. B. GNAM ETAL 2,741,162

ELECTRONIC ANALOG SAFETY FOR AUTOMATIC WEAPONS Filed April 17, 1950 Gordon E1- Gn'um Lufnyecce IE1. H Ed 13 e TIME amma/1 770d F rates ELECTRONIC ANALGG SAFETY FDR AUTOMATIC WEAPGNS Gordon B. Guam, Alexandria, Va., and Lafayette B. Hedge, Wood Acres, Md.

The invention described in the specification and claims may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to electronic control devices and more particularly to an electrical analog in combination with an electronic device which operates to prevent cook oil? of a round of ammunition in an automatic gun. The term electrical analog as used in this invention relates to the electrical circuits used to simulate a physical condition in an automatic weapon.

One object of the invention is an electrical analog in combination with an electronic indicator to furnish a continuous indication of the temperature of a gun barrel.

Another object of the invention is an electrical analog combined with an electronic actuator to automatically efiect certain secondary operations determined by the temperature of the gun barrel as reproduced by the analog.

Another object of the invention is an electronic indicator and control mechanism for an irregularly recurring thermal or similar process.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from the following description and drawings in which:

Fig. 1 is a diagram of the electrical analog and thyratron circuits and associated means connected to an automatic aircraft gun.

Fig. 2 illustrates the temperature and voltage curves.

In gun mechanisms the design of which is such that the firing cycle begins and ends with a complete round of ammunition in the chamber of the barrel and the bolt forward and locked, the barrel temperature is exceedingly high and the chambered round will detonate or cook oil after a lengthy burst or repeated short bursts resulting in damage to both or either personnel and material. Prior developments involved the use of bimetallic thermostats afiixed to or in intimate contact with the barrel together with such circuitry as necessary to initiate upon unsafe indication by the thermostat a gun charger. The difliculty in the employment of a thermostat lies in the fact that it is a relatively sensitive device which must be afiixed to the gun and which in addition to complicating the gun assembly and disassembly, subjects the thermostat to extreme vibration during gun fire accompanied by subsequent unreliability.

Referring now more particularly to the drawings there is-shown in Fig. 1 an automatic aircraft gun I having a barrel 2, a receiver 3 and mounted on one side of said receiver a charger The charger control relay 5' is aflixed to one end thereof for the purpose which will be subsequently disclosed. An electrical contact member 6 mounted on said receiver connects the electrical firing pin of the gun by means of conductors 9 and 10 through means of firing switch 8 to a source of current 7 to fire the chambered round. Closing the firing switch 8 also places a source of current 7a across the coil 11a of the trigger circuit relay 11 and thereby 2,?43152 Patented Apr. 1Q, 1956 energizes the relay. The trigger circuit relay is provided with contact members 12 and 13, and 14, 15, and 16. When the trigger circuit relay is not energized contact members 12 and 13, and 15 and 16 are in engagement with each other, respectively. Contact member 13 is connected to the plate of the thyratron 33 and contact member 12 is connected to one terminal of the coil 17:: of the plate relay 17. The other terminal of coil 17a is connected to the conventional plate battery 18 or any other voltage regulated source of plate current to complete the plate circuit as shown in Fig. 1. The thyratron plate circuit relay 17 is provided with contact members 19, 20, 21, 22 and 23 so arranged that when the relay coil 17a is de-energized, contacts 22 and 223 are separated and contacts 19 and 2% closed while, when coil 17a is energized, contact is effected between 22, 23 and 29, 21, while contacts 19 and 2d are separated. Contacts 22 and 23 control a circuit including a source of voltage 24 and charger control relay 5. Contacts 19 and 20 when closed, complete a circuit including a voltage source 34 and a signal lamp 25 while contacts 28 and 21, when closed, complete a circuit including source 34 and a signal lamp 26 which may be distinctive from lamp 25. Contact members 19 and 20 are engaged when the gun barrel is relatively cool and in this instance close a circuit comprising a battery 34 and indicating means 25, such as a green panel light, in series to indicate that the barrel is relatively cool. Contact members 22 and 23 are in series with a voltage supply 24 and are not in engagement until the barrel temperature has reached the cook on, level. Likewise, members 20 and 21 are not in engagement, but upon call due to barrel temperature they engage closing a circuit comprising the battery 34 and indicating means 26 similar to but distinctive from indicating means 25 to show that the barrel is dangerously hot. A conventional bias means 28 supplies the grid of thyratron 33 with an appropriatebias voltage. The circuit for charging capacitor 2? comprises a source of regulated voltage E which is applied to the capacitor 29 connected to the input of the thyratron through resistor 30 when the contacts 14 and 15 are closed upon energization of relay coil lla through closure of firing switch 8. At the same time contacts 15 and 16 are opened, disconnecting the resistor 31 from the thyratron input circuit. The values of the resistor 30 and capacitor 29 are selected so .that as the capacitor is charged by the voltage source E during the firing period, its voltage increases at the same rate as the rate of the gun barrel temperature increase, as shown by curves A and C in Fig. 2. Curve A representing the temperature rise of the gun barrel and curve C representing the voltage rise of the capacitor are substantially coincident and likewise curves B and D represent the decay of temperature and voltage, respectively, after the firing switch 8 has been released and the resistor 31 shunted across the capacitor.

In operation when the gun barrel is relatively cool the trigger circuit relay contacts 15 and 16, and 12 and 13, shunt the resistor 31 across the capacitor 29 and close the thyratron plate circuit, respectively. The grid of the thyratron is provided with a bias 28 to prevent plate current flow when the potential of the capacitor has been reduced to and below a predetermined value. When the potential of the capacitor is not greater than the bias voltage, no plate current flows and the plate circuit relay contacts 19 and 20 close lighting a green panel light 25 which indicates the gun barrel is relatively cool. To

fire the gun it is only necessary to close the firing switch until the desired burst is accomplished. Closing the firing switch energizes the trigger circuit relay to open the plate circuit, disconnect the shunt resistor 31 from the capacitor and connect the source of voltage E series resistor to the capacitor through resistor 30, and thereby charge said capacitor during the period of burst. By inspection of the curves in Fig. 2, it can be seen that the potential of the capacitor will increase at the same rate as the temperature of the gun barrel. The values of the series resistor 30 and capacitor 29 are selected so as to make the capacitor voltage rise curve C substantially coincident with the gun temperature rise curve A. The cook off temperature is indicated by the coordinate e and the corresponding potential of the capacitor by the coordinate 7. If the burst has been of a duration such that the barrel temperature is at the cook off value as indicated by e on curve and the firing switch released, the trigger circuit relays contacts 12 and 13 will close to complete the thyratron plate circuit, and contacts 15 and 16 will close completing the grid to cathode circuit of the thyratron, but since the potential of the capacitor is now in excess of the grid bias, the thyratron fires and the charge on the capacitor is dissipated by the shunt resistor with the subsequent potential lowering of the capacitor. The voltage decay of the capacitor is in accordance with the selection of the ohmic value of the resistor 31 in combination with the capacitor. The selection in this case is such that the rate of voltage decay is substantially the same as the rate of gun barrel temperature decay.

When the thyratron fires, a current flows through its plate circuit and energizes the plate circuit relay coil 17a,

causing contacts 19 and 20 to open, disconnecting the cool barrel indicator and also causing the contacts 20 and 21 and 22 and 23 to close connecting the hot barrel indicator 26 and energizing the charger control relay 5, respectively. The charger control relay then activates the charger 4 which extracts a round from the chamber of the gun. The charger relay is equipped with a hold device, not shown, which holds the bolt open as long as this charger relay circuit is closed, or until the tempera ture of the gun barrel has fallen below the cook 01f temperature whereupon the charger places a round in the chamber and ceases to extract. As the barrel temperature is lowering, the capacitor is discharging through the shunt resistor and the capacitors voltage is diminishing at the same rate as the temperature of the gun barrel. A vacuum tube voltmeter 32 having its scale calibrated in degrees of temperature is connected across the capacitor to give the operator a continuous barrel temperature reading.

We claim:

1. A safety system for an automatic gun having an electrically actuated round extracting means, comprising a firing circuit, a condenser, and a discharge device, means for applying a voltage to said condenser during periods of closure of said firing circuit, means for applying the condenser voltage to the said discharge device, and means for discharging the said discharge device through the said round extracting means upon opening of the said firing circuit.

2. A safety system for an automatic gun having an electrically actuated round extracting means comprising a firing circuit, a switch to open and close said firing circuit, a condenser, means for applying a voltage to the said condenser when the said switch is closed, a discharge device having the control element thereof connected to said condenser, and means for discharging the said discharge device to actuate the said round extracting means when the said switch is opened. a a

3. A safety system for an automatic gun having an condenser, and means for discharging the said discharge device to actuate the said round extracting means when the said firing circuit is open.

5. In an automatic gun safety system, a firing circuit including, in series, a first source of voltage, a trigger switch and the coil of a first relay, a charging circuit including, in'se'ries, a capacitor, a second source of voltage and contacts closed only by and in response to energization of the coil of said first relay, a thyratron, a cathode to grid circuit for'said thyratron including said capacitor and a source of bias voltage, a plate circuit for said thyratron including in series the coil of'a second relay, a third source ofvoltage and a pair of normally closed contacts opened only by and in response to energi'zation' of the coil ofsaid first relay, a chargerof the type operable to extract around from th'egun, electrical operating means for said charger, and a control circuit including in series electrically actuated round extracting means comprising a and a pair of contacts closed only by and in response to energization of the coil of said second relay.

6. The invention as set forth in claim 5 ,Wherein said charging circuit includes a resistor connected in series with said capacitor through said first relay during condenser charging cycles. 7

7. In an automatic gun safety system, a firing circuit including in series, a trigger operated-switch connecting a first source of voltage simultaneously toan electrically operated firing pin and a'coil of a first relay, a charging circuit including a second source of voltage, a capacitor, 21 first resistor, a second resistor, a thyratronhavinga cathode to grid circuit and a biasing voltage therefor, the

coil of a second relay, and first contacts closed only when the coil of said first relay is energized to connect said second source of voltage in series to said condenser through said first resistance to charge said condenser at a predetermined rate, and second normally closed contacts.

opened only when the coilof said first relay is energized to open a circuit including said thyratron plate, the coil of said second relay, and a source of voltage for said plate, said condenser discharging in series through said' second resistor upon energization of thecoilof said first relay to discharge said condenser at a predetermined rate, a charger of the'type operable to extract a round from the round chamber, electrical operating means for'said charger, a control circuit for said electrical operating means including in series, a fourth source of voltage, a pair of normally open contacts closed only in response to energization of the coil of said second relay connecting said fourth source of current to said electrical operating means, whereby said charger extracts a round from the gun chamber in response to potential from said thyratron which fires when said capacitor potential is greater than said bias potential, said capacitor potential being a a-- logues to gun chamber temperature;

8. In an automatic gun safety system, a firing circuit including, in series, a trigger operated switch connecting a first source of voltage simultaneously to an electrically operated firing pin and a coil of a first relay, a chargingcircuit including, iriseries, a source of regulated voltage, a first resistor, a first relay, a capacitor, a thyratron having a cathode to grid circuit and a biasing voltage therefor, a coil of a second relay connected with-the plate of said thyratron and a source of plate yoltage,.said first relay having a first and second contact closed upon deenergization of said first coil, said first switch in the line between said 'plate and said second coil, said second switch in the line between said condenser and a second resistance through which said, condenser discharges at a source of voltage, a second relay and a charger control relay, said second relay having first normally open contacts therein closed upon energization of said second relay to operate said charger relay to extract a round from the gun chamber, and visual signal means operatively associated with said second relay.

References Cited in the file of this patent UNITED STATES PATENTS Minkler Dec. 12, Wagner Nov. 21, Severance Apr. 2, Wisman et a1. Nov. 5, Catlin Apr. 12, Wilson et a1. May 31,

FOREIGN PATENTS France Apr. 25, 

